The chiral-recognition processes of homoproline (hpro) and [Ir-(pq) 2 (MeCN) 2 ](PF 6 ) (pq is 2-phenylquinoline; MeCN is acetonitrile) are investigated, in favor of formation of the thermodynamically stable diastereomers Λ-[Ir(pq) 2 (D-hpro)] and Δ-[Ir(pq) 2 (L-hpro)]. Moreover, the diastereoselective photoreactions of Δ-[Ir(pq) 2 (D-hpro)] and Δ-[Ir(pq) 2 (L-hpro)] are reported in the presence of O 2 at room temperature. Diastereomer Δ-[Ir(pq) 2 (L-hpro)] is dehydrogenatively oxidized into imino acid complex Δ-[Ir(pq) 2 (hpro-2H 2 )] (hpro-2H 2 is 3,4,5,6-tetrahydropicalinate), while diastereomer Δ-[Ir(pq) 2 (D-hpro)] occurs by interligand C−N cross-coupling and dehydrogenative oxidation reactions, affording three products: Δ-[Ir(pq)(D-pqh)] [pqh is N-(2-phenylquinolin-8-yl)homoproline], Δ-[Ir(pq) 2 (hpro-2H 2 )], and Δ-[Ir(pq) 2 (D-hpro-2H 6 )] [hpro-2H 6 is 2,3,4,5-tetrahydropicalinate]. The C−N cross-coupling and dehydrogenative oxidation reactions are competitive, and the dehydrogenative oxidation reactions are regioselective. By optimization of the photoreaction parameters such as the diastereomeric substrate, solvent, and temperature as well as base, each possible competitive product is selectively controlled. In addition, density functional theory calculations are performed to elucidate the distinctly chiral recognition between proline and hpro with an iridium(III) complex.

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The selective photoreactions under mild conditions play an important role in synthetic chemistry. Herein, efficient and mild protocols for switching the photoreactions of Ir(III)-diamine complexes between the interligand C–N coupling and dehydrogenation are developed in the presence of O2 in EtOH solution. The photoreactions of achiral diamine complexes rac-[Ir(L)2(dm)](PF6) (L is 2-phenylquinoline or 2-(2,4-difluorophenyl)quinoline, dm is 1,2-ethylenediamine, 1,2-diaminopropane, 2-methyl-1,2-diamino-propane, or N,N′-dimethyl-1,2-ethylenediamine) are competitive in the oxidative C–N coupling and dehydrogenation at room temperature, which can be switched into the interligand C–N coupling reaction at 60 °C, affording hexadentate complexes in good to excellent yields, or the dehydrogenative reaction in the presence of a catalytic amount of TEMPO as an additive, affording imine complexes. Mechanism studies reveal that 1O2 is the major reactive oxygen species, and metal aminyl is the key intermediate in the formation of the oxidative C–N coupling and imine products in the photoreaction processes. These will provide a new and practical protocol for the synthesis of multidentate and imine ligands in situ via the postcoordinated strategy under mild conditions.

Comprehensive Summary β‐Amino acids (AAs), homologs of α‐AAs, are important building blocks of biological materials. Herein, chiral recognitions of β‐AAs with Ir(III) complexes are reported, in favor of formation of the thermodynamically stable Λ‐[Ir(pq)2(D‐β‐AAs)] and Δ‐[Ir(pq)2(L‐β‐AAs)] (pq is 2‐phenylquinoline) diastereomers. The photoreactions of [Ir(pq)2(β‐AA)] complexes are observed in an EtOH solution in the presence of O2 at room temperature. The primary β‐AAs complexes, such as rac‐[Ir(pq)2(β‐ala)] (β‐ala is β‐alanine), Δ‐[Ir(pq)2(D‐β‐ma)] and Λ‐[Ir(pq)2(D‐β‐ma)] (β‐ma is β‐methylalanine), Δ‐[Ir(pq)2(D‐β‐pa)] and Λ‐[Ir(pq)2(D‐β‐pa)] (β‐pa is β‐phenylalanine), and rac‐[Ir(pq)2(β‐dma)] (β‐dma is 3,3‐dimethyl‐β‐alanine), are interligand C—N cross‐coupling in situ between pq and β‐AAs ligands. The secondary β‐AA complexes Δ‐[Ir(pq)2(L‐β‐pro)] and Λ‐[Ir(pq)2(L‐β‐pro)] (β‐pro is β‐proline, 2‐(pyrrolidin‐2‐yl)acetic acid) are dehydrogenatively oxidized into imino acid complexes Δ‐[Ir(pq)2(L‐β‐pro‐2Hβ’)] and Λ‐[Ir(pq)2(L‐β‐pro‐2Hβ’)] (L‐β‐pro‐2Hβ’ = 2‐(3,4‐dihydro‐ 2H‐pyrrol‐2‐yl)acetic acid), respectively. Moreover, the dehydrogenative reaction in Δ‐[Ir(pq)2(L‐β‐pro)] diastereomer is regioselective depending on the reaction temperature, affording Δ‐[Ir(pq)2(L‐β‐pro‐2Hβ’)] and Δ‐[Ir(pq)2(L‐β‐pro‐2Hβ)] (β‐pro‐2Hβ = 2‐(3,4‐dihydro‐ 2H‐pyrrol‐5‐yl)acetic acid) at low temperature. The chiral recognitions and photoreactions of Ir(III)‐β‐AAs complexes are much different from the previous observations in Ir(III)‐α‐AAs complexes.

The construction of C−S bonds is of great importance in the field of synthetic and medicinal chemistry. Herein, solvent-induced umpolung reactions from dioxygenation to interligand C−S cross-coupling in bis(cyclometalated) Ir(III) thiolate complexes are reported in good to excellent yields at room temperature. Specifically, the reaction of rac-[Ir(pq) 2 (aet)] (where pq is 2-phenylquinoline and aet is 2-aminoethanethiolate) can be selectively switched to dioxygenation in acetonitrile solution in the presence of O 2 , resulting in the formation of a sulfinato complex rac-[Ir(pq) 2 (aes)] (where aes is 2-aminoethanesulfinato). Alternatively, the reaction in trifluoroethanol solution leads to interligand C−S cross-coupling, affording a rac-[Ir(pq)(pqaet)](PF 6 ) [where pqaet is 2-((2-phenylquinolin-8-yl)thio)ethan-1amine] complex, which generates a new tetradentate ligand in situ. Mechanistically, the formation of electrophilic metal thiyl radicals is proposed as a key intermediate in the interligand C−S coupling reaction. Furthermore, the sequential oxidation of a thioether complex into a sulfoxide complex is also observed at room temperature using H 2 O 2 as an oxidant. Additionally, a new approach for the synthesis of a hexadentate ligand is developed through sequential C−S and C−N interligand coupling of metal thiolate complexes in situ under visible light irradiation in the presence of O 2 .